What is barge-in?

Old phone menus had none of it. You talked, the recording continued, and you waited for the beep like it was 1998.

People interrupt constantly on real calls. A caller who already knows what they want starts talking over the greeting, which is normal behavior rather than rudeness.

Supporting it means listening while speaking and stopping cleanly mid-word when the caller starts, which is harder than it sounds on a noisy line.

Say your greeting runs nine seconds: the business name, a note that the caller is speaking with an automated assistant, and an offer to help. A regular customer calls from her car, and at second three she starts talking: "Yeah hi, I need to move my Thursday appointment."

Without barge-in, the greeting keeps playing over her. She finishes her sentence at second six and hears the greeting end at nine. Then there's silence, because the system caught only half of what she said, and she has to repeat herself, slower and a little annoyed. With barge-in, the assistant stops mid-word at second three and listens, and by second seven it's asking which day suits her better. It's the same caller saying the same words. What separates the two versions is roughly ten seconds, one repeated sentence, and how your customer feels about you at the end of it.

People make small noises to show they're listening. "Mm-hm", "right", "okay" and "yeah" aren't attempts to take over the conversation, and a system that treats them that way will stop talking every few seconds and wait for a request that isn't coming.

Echo is the other false alarm. On a speakerphone or a car kit, the assistant's own voice leaks back into the microphone, and unless that's filtered out it can end up interrupting itself.

You can test both on a demo in about two minutes. Ask a question that produces a long answer and say "uh-huh" in the middle of it. Do the same thing again on speakerphone with the volume up. Cough once. Then interrupt properly, with a real sentence, and see how fast it yields. You're checking that it stops for the sentence and keeps going through everything else.

A caller who starts talking over the greeting is heard rather than waited out, which is what most people do when they already know why they rang.

Keep your greeting short for the same reason. A caller who interrupts a long greeting has already decided it was too long.

Where the assistant and the caller do talk over each other, the transcript shows it, and that is usually a sign the wording needs trimming.